Does the Bible ever comment on Adam and Eve having a female child?
Yes, I believe it does.
Genesis 4:16-17 Then Cain went out from the presence of the Lord and dwelt in the land of Nod on the east of Eden. And Cain knew his wife, and she conceived and bore Enoch. And he built a city, and called the name of the city after the name of his son—Enoch. (NKJV)
Where did Cain’s wife come from? This is a common objection by anti-Genesis folks who believe this “proves” the Bible is wrong. Why? Because the Bible says Adam and Eve were the first people, so how could their son Cain find a wife?
See!!! The Bible is wrong! Told you so!
This question about Cain is often proposed as a “trick question” meant to “stump” a Christian and make the Bible seem flawed. But like all “trick questions” concerning the Bible, there is no trick at all. It is one of the most juvenile arguments I have ever heard, and shamefully, most Christians sit in stunned disbelief when it is thrown at them.
Where did Cain’s wife come from? The answer is obvious and simple. She was his sister or niece, one of the daughters/grandaughters of Adam and Eve.
But that’s incest!! Right? No. Not at that point in time.
In Adam’s day, there were no “laws” about incest, humans lived by their conscience. God had not given laws yet. Additionally, there was no medical reason at that point that would prohibited close relations from marrying and reproducing. The degeneration of the human gene pool had only just begun shortly before with Adam’s first sin and the resulting curse. The genetic degeneration would have been virtually undetectable in the first few generations.
Only the first generation would have needed to inter-marry anyway. After that it would have been cousins, and successive generations would widen the family gap. Still, until God gave the Law, there was no prohibition forbidding inter-family marriage, and for many generations, no medical risks.
Incest only became a sin, once God pronounced it a sin later on after the world was populated. Because of the innate sense of discomfort about reproducing with a family member, its questionable that is was a common practice anyway (my opinion).
Either way, there would have been no medical consequence like there is today with retardation a probability in incest due to genetic degradation.
We make the mistake of thinking that everything in history has always been the same as it is now. When sin entered the human race, it began a corruption and degradation that continues to intensify with every generation. Adam and Eve’s children could intermarry and reproduce without breaking any law or commandment, and without fear of genetic problems.
Cain married one of his sisters, or possibly a niece. And if that is not enough evidence, how about something a little plainer:
Genesis 5:4 After he begot Seth, the days of Adam were eight hundred years; and he had sons and daughters. (NKJV)
That would pretty much settle the question.